It is known that the doors of electric household appliances in which a washing cycle is carried out, in particular those of washing machines/drying machines/dishwashers, are blocked in use in a closed position by a blocking device provided with a safety device which is released only either at the end of the washing cycle or in all cases when the rotating drum of the electric household appliance is either still or turns at a speed which is not dangerous for the user.
The safety devices known from U.S. Pat. No. 6,334,637, for example, include a blocking pawl and a control system for selectively moving the pawl between an extracted position and a retracted position in a through seat of a casing carrying the control system and the pawl itself therein, so that one end of the pawl protruding in the extracted position from the seat, can cooperate in use with a plate of the blocking device of the door, slidingly carried by a support on which the casing of the safety device is snappingly fixable; the support is in turn fixable in use to a carcass of the electric household appliance, by the side of the door to be blocked and so that the sliding plate is adapted to cooperate in turn, in use, with a striker of the door.
The control system includes in turn a first electric actuator device, e.g. a bimetal foil associated with a PTC element (tablet), or thermistor, which when the electric household appliance is running, is adapted to displace the pawl between the extracted and retracted positions, and electromagnetic means for blocking the pawl in the extracted position, in which position it engages a perforation of the sliding plate, thus blocking its transversal sliding on the support and therefore preventing the same from being released from the striker even if the user attempts to force the door into the opening position.
The electromagnetic blocking means include in turn an electromagnetic actuator of the linear type which is actuated in use by a series of single electric pulses upon which the core of the electromagnet rotationally actuates, by means of a ratchet, a gear wheel associated with cam means which selectively block/release the pawl in the extracted position, thus cooperating with a side appendix thereof. Thereby, by means of an appropriate shape of the cam means and the gear wheel associated therewith, the pawl and then the whole blocking device may be blocked, by applying a single electric pulse to the electromagnetic actuator, while two consecutive electric pulses are needed to release them.
The known device described above is complex and costly, as well as large in size.